1. Field of the Invention
The present invention relates to an excavator-hoist including a chassis for supporting an operator""s cab, a drive assembly and a boom carrying at its free end a working tool, with the excavator-hoist further including two pairs of projecting arms connected to opposite end sides of the chassis, respectively, hydraulically operated piston-cylinder means for pivoting the arms in horizontal and vertical planes, and two pairs of motor-driven wheels supported on free ends of arms of respective pairs of arms, with the wheels of both pairs having approximately the same diameter, and the wheels of at least one pair being steerable.
2. Description of the Prior Art
A construction similar to that described above is in German Publication DE 42 19 803AI. It discloses a working tool assembled from a set of prefabricated separate units. The working tool is driven by a stepping or gear drive assembly. The undercarriage includes two connection devices for connecting two, sliding one beneath the other, pairs of hinge supports which are pre-assembled from a set of interchangeable, vertically and horizontally pivotable, wheeled or steady supports, so that the undercarriage is alternatively supported by two wheeled supports and two steady supports or by four wheeled supports. At that, at least two wheels of the pair of wheeled supports are driven and steered with wheel hub motors, with the remaining wheels being provided with parallel guiding means. Further units, which are connected with each other, form a superstructure, which is connected with a support housing by a pivot support, and a boom section secured on a pivot bracket. The object of the German reference is to provide means which would insure an assembly on a work cite of a working aggregate from a set of separate functional constructional units with relatively small expenses. The constructional unit themselves should have a construction which would insure, dependent on the use condition, formation, amplification or retooling of different excavators or movable cranes. E.g., the set described in the German reference permits to convert a simple walking excavator into a wheeled excavator to adapt it to improved driving conditions.
An object of the present invention is an excavator-hoist with an improved mobility.
Another object of the present invention is to provide an excavator-hoist having a compact construction and which can easily be moved.
A further object of the present invention is an excavator-hoist with simple maintenance requirements so that it can be used for digging trenches and, in particular, water-carrying trenches.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing an excavator-hoist of the type described above in which the arms, which support the steerable wheels, have front upwardly offset portions in a vertical plane, with the steerable wheels being carried by offset portions of the steerable wheel supporting arms, and with respective piston-cylinder units, which are provided for pivoting the steerable wheel supporting arms in respective vertical planes, having one of their respective ends attached to the respective arms above pivot axes of the respective arms, and having another of their respective ends attached in respective regions of bottoms of the respective arms. According to a particularly preferred embodiment of the present invention, the steerable wheel supporting arms have a box-shaped or downwardly-opening U-shaped profile, with each of the arms having a recess formed in a vertical longitudinal central plane of the arm for accommodating the arm-pivoting piston-cylinder unit. This measure permits to lift the bent-off arm rather high, with a sufficiently large free space still being available for a sidewise movement of the boom. At that, the piston-cylinder unit is adequately protected.
According to a further development of the present invention, there is provided a pair of L-shaped pivot levers for supporting the steerable wheel, with a horizontal leg of each pivot lever carrying an upright bolt an axis of which is located in a radial central plane of a respective steerable wheel, the bolt being rotatably received in a bearing bore provided in a free end of a respective steerable wheel supporting arm and located approximately in a vertical longitudinal central plane of the respective steerable wheel supporting arms. When the excavator-hoist moves along a muddy and wet bottom, the steerable wheel, together with the vertically offset portions of the arm, form only a small surface which displaces along the muddy and wet bottom. On the other hand, when the wheels are positioned in a manner known from the state of the art, the wheel, together with their carriers located sidewise with respect to the supporting arms, present increased resistance surfaces which act as plowshares against the muddy mass when the excavator-hoist need to be moved.